The Ostrovnoy naval base started operation in the 1960s for the refuelling and storage of spent nuclear fuel of nuclear submarines. It is one of the sites identified by the Strategic Master Plan (SMP) under the Northern Dimension Environmental Partnership (NDEP) as highly important and requiring urgent measures to reduce possible negative effects on the environment. At present the site serves as a facility for temporary storage of radioactive waste (RAW) and spent nuclear fuel (SNF). Preliminary radiological surveys to design remediation works at the site were conducted in 1999. The surveys did not cover the existing open Pad (for solid waste) and Building 19 (tanks for liquid waste). A review of the available radiological data revealed it inadequate and insufficient for the planning of the remediation works.
The purpose of this project (ref AP 126.96.36.199.2) was to obtain the missing information about the radiological situation at the site and to assess and propose the most viable technical solutions for the radioactive waste treatment, conditioning, further storage and disposal activities. The project had to provide assistance to the Decommissioning of Nuclear Installations Department of the Ministry for Atomic Energy of the Russian Federation (MINATOM).
The project aims to the analysis and collection of information needed to catalogue the material stored at the Open Pad for Temporary Solid Waste Storage (Abbreviated PVHTRO in Russian) at Gremikha bay SMB. The objective further includes an assessment of physical conditions of storage containers (and bulk RAW) and other elements which is an essential input for the development of the remediation plan and strategy. Due to the harsh environment (high radiation level, insufficient information on stored radioactive material, presence of unknown toxic substances), in which the work has to be done, additional emphasis is put on the radiological and health protection of workforce and the population during implementation of this project.
This project aims to perform a comprehensive engineering and radiation survey (KIRO in Russian abbreviation) of the Open Pad of Gremikha bay SMB. The survey shall collect specific information on material stored at the Open Pad along with radiation characteristics and engineering conditions of each of the elements on the Open Pad and the Open Pad as a whole. This information is then to be used in planning and execution of remediation activities of the Open Pad: conditioning and/or relocation of the material stored. The results of this project will be the basis for further activities to be implemented in the overall area of Gremika bay SMB by the Beneficiary organizations in the frame of other bilateral (French) and multilateral programs (NDEP).
Finally, the specific objective of the project includes also preparation of an extensive report, documenting the activities done and providing the results of the survey, to enable planning and implementation of remediation activities. The documentation to be prepared within this project shall be sufficient to enable development of full design documentation for the removal of radioactive material from the Open Pad and its transfer to temporary shelters.
Review and enhancement of personnel protection measures.
Due to a high radiation level at the Open Pad and its surroundings, KIRO operations involve high risk for personnel. The major hazard is posed by intense gamma sources found at the Open Pad (with radiation levels in some places as high as a few hundreds mSv/h). Migration of radionuclides from leaking containers with SRW kept at the Open Pad causes a significant radioactive contamination of the Open Pad itself and its adjoining areas.
To protect personnel during KIRO operations, there were used occupational and radiation safety facilities existing at SevRAO Branch No.2, including Radiation Safety Services, sanitary stations, Radiochemical Laboratory and available personal protective equipment. In addition, the following administrative/organizational and technical measures were implemented in accordance to Annex III to the Contract, Section “Review and enhancement of personnel protection measures”:
- Analysis of existing safety facilities and arrangements at the site of conducting KIRO operations at the Open Pad, which yielded that existing documents complies with the requirements of the Russian Federation regulations. New documents and modifications of existing documents were suggested, and some safety instructions with close expiration dates were extended
- Developing of additional administrative arrangements for defining and controlling occupational safety for KIRO activities;
- Specifying and delivery of additionally needed personal protective equipment;
- Specifying and delivery of additionally needed equipment for the dosimetry service and materials for radiation shielding;
- Specifying and delivery of additional materials and equipment for the radiochemical laboratory, and instruments to be used during the KIRO survey;
- The materials and equipment mentioned above was specified and delivered as scheduled.
- Commissioning of two mobile sanitary stations manufactured under a contract with CEA, France and delivered to the Gremikha site for the Open Pad activities;
- Commissioning of a post for radiation control of personnel and storage/collection of used personal protective equipment (dose control point) in the vicinity of the Open Pad;
- (Since there are no clean water supply and sewage removal lines in the vicinity of the Open Pad, the delivery of clean water and removal of sewage is performed by using mobile tanks trailers to be carried by a lorry.
The mobile facilities mentioned above were designed, manufactured, assembled and delivered as expected.
Commissioning of a tower with a gamma camera to be used during the KIRO survey, to map and monitor the radiation situation at the Open Pad. This equipment allows taking measurements at the heights of 5, 10, 15 and 20 m.
Design, delivery and temporary installation of radiation shielding on a cab of a truck crane. While the operations in the Open Pad are subjected to high gamma radiation, the use of a truck crane improves the efficiency and reduces the collective radiation dose. However, in some instances, additional shielding is required. This additional shielding was designed, manufactured and delivered according to schedule.
Regarding the preliminary radiation and engineering survey of the Open Pad, it was conducted in three main parts:
1) Initial radiation survey in close vicinity of Open Pad and its concrete fence, including measurement of concentration of aerosols, preliminary engineering survey of the concrete fence and visual inspection of objects placed in the Open Pad. The survey was performed during September and October 2006, examining the radiation situation around the Open Pad (gamma radiation dose rates and beta particles flux density), soil sampling, concrete surface contamination sampling, and radiological analysis of aerosols in the air. This part showed that works in close vicinity of the Open Pad can be performed in compliance with the Russian Federation regulations and the IAEA recommendations. The data obtained (including the presence of Cs-137, Sr-90, Co-60 and Eu-152) allowed to plan the operations near de Open Pad safely as well as to design the documentation for the remediation of the Open Pad.
The preliminary engineering survey of the Open Pad in Gremikha consisted in acquisition and study of historical records of objects stored in the Open Pad, (including containers, large size metal structures, and bulk RAW); photography and charting of the objects found, engineering evaluation of the concrete wall condition, visual assessment of the physical condition of the RAW and SNF containers, processing and preparation of the acquired data for input into the radiation and engineering survey database. The results of the assessment have been an inventory of objects on the Open Pad, which were found to be with metal corrosion and damages in concrete walls (including the exposure of the armour bars). Most of the concrete blocks strengths are on or above their design value, except for some specific blocks. Their lower strength is attributed to inadequate fabrication. The adjacent walls are designed for biological shielding, so they cannot be used as bearing structure for hoisting equipment or observation platforms.
2) Measurements and detailed mapping of gamma-radiation Equivalent Dose Rate (EDR) at the Open Pad, as well as finding and shielding of intensive radiation sources at the Open Pad.
Detailed measures allowed to have a map of the gamma dose distribution on the Open Pad as well as the location of 13 intense radiation sources. The strategy and equipment used minimized the exposure to the workers. Subsequent calculations and analysis recommended to shield transport container no 113 and container K15. Additionally, a few high radiation fragments were moved to an empty transport container. These measures aimed at minimizing worker exposure during subsequent operations.
Several additional shielding lids were installed in intense gamma radiation sources.
The collective dose, related to these activities were 17 % less than estimated, and individual doses were significantly lower than the limits of the Russian Federation regulations.
3) Radiation and engineering survey of RAW and SNF at Open Pad.
The radiation and engineering survey of RAW and SNF at the Open Pad has been done by different means:
- Measurement of radioactivity in the ground and structures at the Open Pad. 46 samples were taken inside the concrete enclosure, 2 samples of concrete of the ground pavement, 32 samples of soil drifts on the ground, and 10 samples of concrete on the inside of the lower blocks of the enclosure. The analysis of the samples showed that all the soil is qualified as intermediate level waste. Concrete blocks are qualified as low level waste except blocks in the rear part, which are intermediate level waste.
- Radiological and radiometric characterization of containers with SNF and RAW, using dose measurements above the individual objects and measurement of gamma spectra of the individual objects. The results showed EDR rates at 1 m from th surface between a few mSv/h and several tens of mSv/h. The most intense radiation sources are containers TK-35 and TK-111, and concrete containers Бет2 and Бет4, and the measured spectra are characterized by predominance of Cs–137. Eu-152 lines were identified in amplitude distributions obtained for containers Бет2, Бет4, Бет6, Суз1 and Суз4.
- Radiation measurements to determine dose rates distribution along containers with SNF.. The shape of the distribution of EDR produced by SNF stored in a container can give indication of the physical condition of the fuel.
- Measurements of radiation dose along vertical axis of containers with SNF by solid state dosimeters.
- Evaluation of mechanical state of SF assemblies in containers TK-6 by a dynamometric method. The evaluation indicated damaged SFA.
- Works on detection of damaged SNF inside containers at the Open Pad based on Radon emissions. Radon is accumulated in insignificant amounts, so this method is disregarded to identify damaged fuel.
- Checking containers with SNF and RW for water inside them. A method based in a conductive liquid was developed to determine the water level inside the containers. Several of them showed water level.
- Analysis of water samples from containers kept at the Open Pad for radionuclide composition. Several containers' water comprised Sr-90, Cs-137 and Am-241
- Visual inspection of the interiors of containers with RAW using a TV surveillance system. Preliminary conclusions were that the Бет7 container is filled with SRW that according to the classification adopted in Russia are qualified as compactable combustible waste; the Бет7 container also holds solid metal radioactive waste, and the presence of snow in the container points to high probability that water representing LRW may be found at the container bottom.
- Engineering survey of containers with SNF and RW and other objects located at the Open Pad for determination of their weight, sizes and design. The outcome of this task is a table with an estimation of the size and weight of the containers.
- Engineering survey of condition of containers at the Open Pad. The conditions of storage of containers with SNF at the Open Pad do not meet safety requirements. The containers are constantly exposed to corrosive medium and atmospheric precipitation. Requirements of technical specifications have not been observed during the use of containers of type 6 and type 11. Main findings are: damage of the anticorrosive (paint) coat on the surfaces of containers, various damages of lid assemblies of containers, lost of standard lids that are replaced with improvised devices, lack of tamper indication, damaged bodies, lack of baskets (spent fuel loaded as bulk), wrong insertion of SFA into container, water intrusion, inside corrosion, impossibility to remove the lids, SFA with defects that preclude the use of standard tools, etc.
Survey conditions of reinforced concrete containers. These containers show local damages in the protective concrete cover, which resulted in the exposure and corrosion of the reinforcing bars; as well as passing cracks.
Metal containers and large size solid waste show general corrosion and mechanical damages.
- Evaluation of subcriticallity of containers with SNF at the open Pad. Subcriticallity was evaluated (confirmed) by experimental procedures as well as with calculations. It is clear from results of the calculations that even if there is water in the container and all SFA failed with fuel powder accumulated on the container bottom, the K(eff) in stationary containers will for certain be less than 0,3. There is a risk of criticality only in case of a mechanical action upon containers resulting in shaking the fuel off the bottom and formation of a homogeneous fuel/water mixture.
The evaluation of the condition of containers and large-size solid radioactive waste resulted in the identification of safety concerns in the fields of design, amount and spacing of the fuel load, lifting pins strength, status of the lid and bottom with respect to the container body, etc. The following recommendations for the transportation apply to containers and large-size solid radioactive waste:
Before removing of SFA from the Gremikha TSF site, arrangements shall be made to ensure further safe storage of SFA in containers of type 6 and 11 at the TSF site. To this end, it is necessary to remove water from containers of type 6 and 11 and close the containers with lids preventing atmospheric precipitates from getting inside the containers or place the containers with SFA in casks intended for transportation and storage of SNF and transfer the casks into a special shelter for temporary storage.
Observed defects and damages of the reinforced concrete containers ЖБе1 – ЖБе3 and concrete containers Бет 1 – 8 have a local nature; however, the load-bearing ability of the container lifting fixtures (lifting pins) cannot be determined due to the lack of design and as-built documents for the containers. The containers shall be transferred to a SRW sorting and treatment area using special grips.
Containers, reactor water clean up filters, drums and bulk SRW with significant surface contamination shall be transferred to the site of their treatment, conditioning or storage in special shipping containers.
The analysis of efficiency of works on personnel radiation safety assurance was done by scanning the Open Pad after the precautionary actions of shielding the high radiation sources were taken. The results showed that over half the Open Pad area, the EDR was reduced about 5 times, and over one quarter of the Open Pad area, about 8 times. Additional technical and organizational measures were taken, like the installation of mobile sanitary stations and the dose control post, radiation shielding on the truck crane cab, the installation of the telescopic tower with the gamma camera, the equipment for personal protection and dosimetry service, the organization of dose monitoring, preparation of documents, etc. At the end, the collective equivalent dose for personnel involved in the works was about 30 mSv, with a maximum individual equivalent dose of 4.1 mSv.
It is declared in summary that the main tasks of the Contract were completed: additional measures on radiation protection of personnel implemented under the Contract made it possible to conduct operations at the Open Pad with observance of RF radiation safety norms and IAEA recommendations. The method of successive suppression of most intense radiation sources allowed reducing the radiation level at the Open Pad in average by a factor of 5, and in some points more than 10 times. This made it possible to significantly increase the time when personnel could perform operations at the Open Pad. This method can be used also at the subsequent stages of the Open Pad remediation activities. KIRO was performed at the Open Pad, and main initial data were obtained, required for development of further design documentation for removal of SNF and RW from the Open Pad – Declaration of Intent (DON) and Investment Justification (OBIN). Procedures developed under this Contract (for example, procedures for EDR measurements at the Open Pad, LRW sampling procedures, procedures of TV examination of interiors of containers with SRW and a number of other procedures) are recommended for use at the following stages of Gremikha site remediation activities. KIRO results were entered in the Gremikha Information and Analysis System (IAS) DB.